Labour is heading for opposition unless cabinet ministers stop manoeuvring for position, the party’s general election co-ordinator warned last night.

Douglas Alexander protested that the infighting had angered and dismayed Labour activists who wanted ministers to concentrate on steering Britain through the recession.

His candid admission of the tensions around the cabinet table follows a week of growing speculation about Gordon Brown’s successor after the election.

Harriet Harman, the deputy Labour leader, has been accused by cabinet colleagues of undermining Mr Brown by appearing to position herself for a future leadership bid.

Ed Balls, the Schools Secretary, has faced charges that he is raising his profile for the same reason, while Alan Johnson, the Health Secretary, is being championed by many Labour MPs for being best-placed to take on David Cameron. Yvette Cooper, the Treasury Chief Secretary and Mr Balls’ wife, has even been floated as a surprise candidate for the leadership.

Mr Alexander, who is also the International Development Secretary, revealed his frustration over colleagues’ jockeying for position as he warned that it was demoralising for Labour activists.

Delivering a plea for unity, he said: “The many party staff I have met this week who, with our members, will be on the front line of that campaign, want the direction and focus of the Cabinet’s efforts to be getting Britain through the downturn and working together to secure a Labour victory.

“All of us should remember the words from our party’s constitution, on the back of our membership card: ‘By the strength of our common endeavour we achieve more than we achieve alone.’”

Mr Alexander, who was speaking in his Paisley constituency, said: “When the general election comes, securing a fourth term will be difficult but do-able. The task of securing that fourth term will require unity, effort and innovation.”

Mr Brown is expected to demand unity in a cabinet meeting to be held on Monday outside London. Ministers will then be dispatched on a series of visits and photocalls where they will stress their commitment to concentrating on tackling the recession.

Mr Alexander’s rebuke came after Hazel Blears, the Communities Secretary, also warned of a backlash from the voters if the feuding continued.

“All this political positioning just helps the Tories,” she said. “My message to my colleagues is simple: get a grip. Our first loyalty is to the British people. If they think that we are more interested in our own jobs than theirs, they will not forgive us. If the mindset is all about what happens after some future election defeat, then the game’s up.”

The Justice Secretary, Jack Straw, was named as the public’s first choice to succeed Mr Brown. He was chosen by 19 per cent of people polled by PoliticsHome.com.

The Foreign Secretary, David Miliband, was named by 15 per cent, followed by 10 per cent for Mr Johnson. Ms Harman, who has insisted that there is no “shred of truth” in suggestions that she is positioning herself to succeed Mr Brown, was selected by 5 per cent.

The feuding comes as polls provide further evidence that the “Brown bounce” has collapsed as the recession deepens. On current levels of support, Mr Cameron is heading into Downing Street, with a majority somewhere between 100 and 200.

Labour’s nightmare scenario is that the party comes third behind the Liberal Democrats in the local elections and European elections in June. That could trigger speculation of a final bid to unseat Mr Brown, in what would be an effort to limit the damage in the general election, which must be held by June 2010.